More generally, a potentially difficult point in Zendo (and other realms) is "vacuous fulfillment," of which an example would be furnished by the BN "... all the yellow pyramids are mediums": does a Koan with no yellow pyramids qualify? Most mathematicians and computer programmers would say that it does, since there are no non-medium yellows present. However, it has been my observation that people encountering this idea of "vacuous fulfillment" for the first time often choke on it, and I would not want anybody's first-time choke to occur when they were playing in a Zendo game that I was Mastering. Brian __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com